1. Field of the Invention
The present invention relates to an array substrate, a method of manufacturing the array substrate and a liquid crystal display apparatus having the array substrate. More particularly, the present invention relates to a transmissive and reflective type array substrate for preventing light leakages, a method of manufacturing the array substrate and a liquid crystal display apparatus having the array substrate.
2. Description of the Related Art
Generally, a photosensitive material for patterning an oxidation layer, a metal layer, a semiconductor layer, etc. is widely used in a process of manufacturing a semiconductor device or a liquid crystal display apparatus.
The liquid crystal display apparatus includes an array substrate having a plurality of thin film transistors, a color filter substrate having a plurality of color filters, and a liquid crystal layer interposed between the array substrate and the color filter substrate.
The liquid crystal display apparatus may be classified into a transmissive type liquid crystals display apparatus that displays images by using an artificial light, a reflective type liquid crystal display apparatus that displays images by using an ambient light, and a transmissive and reflective type liquid crystal display apparatus that has merits of the transmissive type liquid crystal display apparatus and the reflective type liquid crystal display apparatus.
FIG. 1 is a schematic cross-sectional view showing a conventional array substrate for a transmissive and reflective type liquid crystal display apparatus.
Referring to FIG. 1, a conventional array substrate for a transmissive and reflective type liquid crystal display apparatus includes a transparent substrate 10, a data line 20, an organic insulation layer 30, a pixel electrode 40 and a reflective layer 50. An image signal is transferred via the data line 20. The organic insulation layer 30 is formed on the transparent substrate 10, such that the organic insulation layer 30 defines a reflective region R and a transmissive region T. The pixel electrode 40 is formed on the organic insulation layer 30, and the pixel electrode 40 receives the image signal. The reflective layer 50 is formed on the pixel electrode 40 or on the organic insulation layer 30 to reflect an ambient light.
The organic insulation layer 30 is formed in the reflective region R, but not formed in the transmissive region T. Therefore, a light Al generated from a backlight passes through the transmissive region T, and an ambient light Nl is reflected on the reflective layer 50. Liquid crystal molecules are disposed over the pixel electrode 40 and the reflective layer 50.
Characteristics of displayed images depend on an arrangement of the liquid crystal molecules, and response of the liquid crystal molecules are changed in accordance with electric fields that are applied to the liquid crystal molecules. Therefore, a process of manufacturing the liquid crystal display apparatus includes an alignment process for uniform alignment of liquid crystal molecules.
The alignment process includes a coating process for coating an alignment film, and a rubbing process for aligning the liquid crystal molecules according to a pretilt angle. When the rubbing process is not uniform throughout the alignment film, the alignment of the liquid crystal molecules is irregular to induce a locally irregular arrangement of the liquid crystal molecules. In case of the transmissive and reflective type liquid crystal display apparatus, above described problems become more serious.
As shown in FIG. 1, liquid crystal molecules are arranged in accordance with a rubbing direction Rd, such that the liquid crystal molecules form a pretilt angle. However, even when rubbing grooves are uniformly formed via the rubbing process, the pretilt angle of first and second inclined portions (or boundary regions) ‘A’ and ‘B’ is not uniform. That is, liquid crystal molecules of the reflective region R and the transmissive region T maintain a uniform pretilt angle, but pretilt angle of liquid crystal molecules disposed in the first and second inclined portions ‘A’ and ‘B’ is not identical with the uniform pretilt angle due to an inclination. As a result, a light generated from a backlight assembly leaks through the first and second inclined portions ‘A’ and ‘B’ to induce an inferiority of a display quality.
FIG. 2 is a schematic plan view of the conventional transmissive and reflective type liquid crystal display apparatus showing a light leakage caused by an abnormal pretilt angle. In FIG. 2, rectangular shape that is not hatched represents the transmissive region ‘T’ of FIG. 1, and ‘CNT’ represents a contact hole through which drain electrode of a switching device and a pixel electrode are electrically connected to each other.
As explained above, a light leaks through a boundary region ‘E’ of the transmissive region ‘T’ and the reflective region ‘R’. Especially, the light leaks much at the boundary region ‘E’ between the reflective region and the transmissive region arranged in that sequence along a rubbing direction Rd.
Furthermore, when the transmissive and reflective type liquid crystal display panel is used as a touch screen panel, a display defect caused by moisture may occur as well as the light leakage. When the touch screen panel is compressed, electric fields of the boundary region becomes unstable to induce an abnormal arrangement of the liquid crystal molecules. Therefore, a fatal light leakage occurs, so that an afterimage remains at the boundary region and moisture gathers at the surface of the touch screen panel.
As described above, the light leakage caused by an abnormal arrangement of liquid crystal molecules disposed in a boundary region between a reflective region and a transmissive region comes out as problems.